Quantitative assessment of serum and urinary polyclonal free light chains in patients with chronic kidney disease.
OBJECTIVE
Monoclonal free light chains (FLC) frequently cause kidney disease in patients with plasma cell dyscrasias. Polyclonal FLC, however, have not been assessed in patients with chronic kidney disease (CKD) yet could potentially play an important pathologic role. This study describes for the first time polyclonal FLC in patients with CKD.


METHODS
A sensitive, quantitative immunoassay was used to analyze serum and urinary polyclonal FLC in 688 patients with CKD of various causes.


RESULTS
Serum kappa and lambda FLC concentrations increased progressively with CKD stage (both P < 0.001) and strongly correlated with markers of renal function, including cystatin-C (kappa: R = 0.8, P < 0.01; and lambda: R = 0.79, P < 0.01). Urinary FLC concentrations varied significantly between disease groups (kappa: P < 0.001; lambda: P < 0.005) and also rose significantly with increasing CKD stage (both FLC P < 0.0001). Urinary FLC concentrations were positively correlated with their corresponding serum concentration (kappa: R = 0.63; lambda: R = 0.65; both P < 0.001) and urinary albumin creatinine ratio (kappa: R = 0.58; lambda: R = 0.65; both P < 0.001). The proportion of patients with abnormally high urinary FLC concentrations rose with both the CKD stage and the severity of albuminuria.


CONCLUSIONS
This study demonstrates significant abnormalities of serum and urinary polyclonal FLC in patients with CKD. These data provide the basis for studies that assess the contribution of polyclonal FLC to progressive renal injury and systemic inflammation in patients with kidney disease.
Hutchison
Colin A
CA
Renal Unit, University Hospital Birmingham, Birmingham, UK. cah692@bham.ac.uk
Harding
Stephen
S
Hewins
Pete
P
Mead
Graham P
GP
Townsend
John
J
Bradwell
Arthur R
AR
Cockwell
Paul
P
D000368:Aged; D000419:Albuminuria / Q000097:blood / Q000276:immunology* / Q000503:physiopathology / Q000652:urine; D015415:Biomarkers / Q000097:blood / Q000652:urine; D002908:Chronic Disease; D003404:Creatinine / Q000097:blood; D005919:Glomerular Filtration Rate; D006801:Humans; D007118:Immunoassay; D007145:Immunoglobulin kappa-Chains / Q000097:blood / Q000652:urine; D007146:Immunoglobulin lambda-Chains / Q000097:blood / Q000652:urine; D007674:Kidney Diseases / Q000097:blood / Q000276:immunology* / Q000503:physiopathology / Q000652:urine; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D011446:Prospective Studies; D012189:Retrospective Studies; D012720:Severity of Illness Index
D015415:Biomarkers; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D003404:Creatinine